A comprehensive study of near-wall turbulence for developing effective hole cleaning strategies

点击翻译按钮获取中文摘要

Effective transport of drilled solids is essential for the successful drilling of horizontal wells. Insufficient cuttings removal causes costly problems such as pipe sticking, excessive torque and drag, difficulties in casing/cementing and logging. The study of solids transport in pipes and annulus is also pertinent to the designing of other field operations such as: proppant transport in hydraulic fracturing; cleaning of sand from production wells; and pipeline transport of oil sands. A long occupied central position in solids transport theory assumes that critical bed shear stress initiates the motion of a particle lying on a bed of sediments. However, recent studies have shown that near bed turbulent fluctuations and the random exposure of solid particles to the flow make it possible for particles to move - even at very low values of the mean bed shear stress. Other studies indicate that the momentum fluxes in longitudinal and vertical direction may be more important in solids transport than the shear stress. Therefore, models for solids transport in pipes and annuli should not be developed based on shear stress alone, as most of the current transport models generally are.The main objectives of this research are to conduct experimental and theoretical studies: i-) to determine the effect of local turbulent burst/ sweep actions (dominating the near wall regions) on the particle deposition and/or re-entrainment; ii-) to observe and quantify the particle deposition/removal process occurring at the bed-slurry interface; iii-) to analyze the controlling forces and offer a comprehensive (mechanistic) model which can be used for the development of effective solids transport strategies in pipes and annuli. Any improvement in solids transport process could particularly benefit Western Canadian heavy-oil production, which extensively uses horizontal wells. These reservoirs are predominantly unconsolidated; as a result, drilling, completion and recovery operations are often prone to excessive sand production, deposition and accumulation along the long horizontal wellbore sections. Industry's capacity to operate safely and economically in such reservoirs will benefit tremendously from a full-scale experimental research such as the one proposed in this study.